This Program Project deals with the heart, the lungs and their interplay. Comprising this research effort are several distinct elements: control of breathing, regulation of cardiac performance, comparative physiology and pulmonary edema. Previous research has been instructive in developing models for investigation. Currently, the program is tending more to fundamental biologic problems on the one hand and to the applications of the results obtained in experimental models to human disease on the other. With respect to the fundamental studies, a major emphasis is being placed on neurophysiology and biochemistry using the experimental models that have been standardized over the years in this laboratory. With respect to the applications of experimental results to human physiology and disease, the most expansive activity has been with human exercise exploring the compensatory mechanisms during heart failure and pulmonary insufficiency and attempting to test the effect of a variety of interventions on cardiac and pulmonary performance. In recent years, the interdependence of the heart and lungs has again become a focus of major interest. Using sophisticated computer technology, a series of studies is underway to integrate the observations on the heart and lungs into a coordinated model that will describe the performance of the cardiorespiratory system.